1. Field of the Invention
The present invention relates to a liquid flow detector of the type associated with a drip chamber formed by a transparent cup-shaped container. An inlet tube extends into the drip chamber and includes a nozzle disposed in the upper portion of the container. The liquid collected in the container flows from the base of the container via an outlet tube under the action of a peristaltic pump disposed in the outlet tube.
2. Description of the Related Art
Detectors of known type are applied to drip chambers and detect the flow of liquid by means of optoelectronic sensors which comprise a photoemitter and a photodetector defining an optical path which intersects the flow of liquid. Flow detectors of known type also comprise an electronic unit which receives as input the signal supplied by the photodetector in order to ascertain whether the liquid is flowing into the container.
Moreover, detectors of known type are separated into two classes depending on the characteristics of the liquid flow (continuous or in droplets). In the first crass of detectors of digital type, the electronic unit counts the number of pulses of the input signal (caused by the droplets falling from the nozzle) in order to ascertain the quantity of liquid flowing into the container. The first class of detector is not able to monitor the flow of liquid when it is continuous as the pulses of the input signal are missing.
In the second class of detectors of analog type, the electronic unit dectects the amplitude of the input signal which is a function of the quantity of liquid falling from the nozzle and compares it with a reference level in order to measure the flow of this liquid. This second class of detector is highly influenced by the characteristics of the container and the condition of the sensor and provides an incorrect reading when the container has yellowed because of wear or age. The presence of vapours in the container may also have an adverse effect on the measurement.